1. Field of the Invention
This invention relates to overhead cranes for handling containers and particularly to an overhead crane having a bridge mounted for rotational movement on its trolley to handle containers which are not aligned with the axis of the crane.
2. Description of the Prior Art
Overhead cranes are commonly utilized to lift, lower and transport containers from various vehicles, from vehicles to storage areas, from ships to vehicles, and the like. An overhead crane generally employs a movable bridge under which a grappler device is suspended through a cable or rope system for attachment to containers of standard design. It is a common problem in the handling of cargo containers that the crane is moved into a position at which its longitudinal axis does not coincide with the alignment of the container beneath the bridge. Since the grappler is generally oriented symmetrically with the crane frame, misalignment between the load and grappler will then occur. To properly handle cargo containers in such a situation with known equipment, the crane must be moved and reoriented so that proper alignment of the cargo with the grappler is achieved. Although it is possible to a limited extent to handle containers which are misaligned with the crane by present designs, it is a common problem that the container begins swaying or other movement from forces induced from the hoist system or even the rope upon the pulleys of the hoist system may become disengaged and cause possible damage to the container due to impact. Accordingly there is a longfelt need to provide an overhead crane apparatus having the ability to safely handle misaligned cargo containers without the necessity of maneuvering the crane to an appropriate parallel alignment with the containers being handled.